So-called ultrahigh molecular weight ethylene polymers, which have extremely high molecular weight, are excellent in impact resistance, abrasion resistance, chemical resistance, strength and the like, as compared with general-purpose ethylene polymers, and thus have excellent characteristics as engineering plastics.
Such ultrahigh molecular weight ethylene polymers are known to be obtained by using publicly known catalysts such as so-called Ziegler catalysts composed of a halogen-containing transition metal compound and an organometallic compound, and magnesium compound supported catalysts as described in JP03130116A (Patent Document 1), and JP07156173A (Patent Document 2). Recently, in terms of production efficiency and the like, ultrahigh molecular weight ethylene polymers are usually produced using highly active catalysts such as magnesium compound supported catalysts and the like.
On the other hand, it is said that ultrahigh molecular weight ethylene polymers are not suited for melt molding, which is a general resin molding method, because of their high molecular weight. For this reason, molding methods have been developed such as a method in which an ultrahigh molecular weight ethylene polymer is gelled and then molded, and a solid phase drawing method in which ultrahigh molecular weight ethylene polymer particles are bonded by pressure with each other at a temperature of not more than the melting point, and are then drawn. Such methods are described in Patent Document 2, JP09254252A (Patent Document 3), JP63041512A (Patent Document 4), and JP63066207A (Patent Document 5) and the like.
Patent Document 1: Japanese Patent Application Laid-Open No. H3-130116 (JP03130116A)
Patent Document 2: Japanese Patent Application Laid-Open No. H7-156173 (JP07156173A)
Patent Document 3: Japanese Patent Application Laid-Open No. H9-254252 (JP09254252A)
Patent Document 4: Japanese Patent Application Laid-Open No. S63-41512 (JP63041512A)
Patent Document 5: Japanese Patent Application Laid-Open No. S63-66207 (JP63066207A)